1. Field of the Invention
This invention pertains to a mixing device for mixing a food or beverage concentrate and diluent together, and to a housing for such a mixing device.
2. Prior Art
The prior mixing devices of this type have required a considerable amount of height. A specific prior device was 5.2 inches (132 mm) high. The total height of a dispensing machine is a directly proportional function of the height of the mixing device. For example, a dispensing machine must have height sufficient for insertion of a cup under the mixing device, for the mixing device, and for powder canisters to feed concentrate into the mixing device. The taller the mixing device, the taller the dispensing machine and the shorter the mixing device, the shorter the dispensing machine.
The materials required and cost of structure and cabinetry are influenced by the total height of the dispensing machine and therefor can be and are influenced by the height of the mixing device.
The prior mixing devices have been rather high speed, for example they have operated in the range of 11,000 to 14,000 RPM. Consequently, these mixers have a high frequency whine, and make a considerable amount of air noise from the whirling impeller and from spattering of diluent hit and slung at high speeds by the impeller.
The prior mixing devices have also had short seal life and seal burn out problems. Replacement of seals has been a problem as a mixer base usually has required removal from the dispenser in order to replace a seal. Failure of a shaft seal has usually destroyed the drive motor as mixing impellers have been mounted directly on the drive motor shaft and leakage past the seal has gone into the motor.
Sanitation has been a problem with the prior mixing devices for several reasons. Firstly the shaft seal has not been removable and washable save for complete replacement. The impeller drive shaft was not cleanable at the area of the shaft seal. The prior mixing devices also have a tendency to blow powdered concentrate around the inside of the dispensing machine. The prior mixing devices tend to indiscretely and randomly blow air out of either the inlet or outlet; typically both the inlet and outlet to the mixing impeller have been radial apertures and air flow could go either way when the impeller was rotating. When air is blown out of the inlet, powder is blown away from the inlet and then subsequently settles like dust on the interior of the dispenser.
Reverse flow of air has another adverse side effect, specifically steam from hot diluent water is blown back around the powder concentrate canister. Concentrate powders are hydroscopic and tend to cake up and plug the powder dispenser, tend to cake up and drop off in chunks giving an erratic concentrate to water mixture and giving chunks of concentrate in the finished beverage or food, and are very unsightly.
Elaborate structures have been devised to protect the powder canister from steam and airflow. Some of these structures are baffles, positive ventilation fans, and hot air pipes. It will be appreciated both the fans and hot air pipes require electrical energy consumption.
Upward flow of steam from the prior mixing devices immediately after a dispensing cycle has been a problem for at least two reasons. Firstly the prior mixing devices have not drained hot water fast enough or well enough and residual hot water in the mixing devices would tend to steam off and go upward. Secondly, the remaining hot water and heat in the mixing device tends to effect upward rising of the steam in a reverse flow when the mixing device is turned off. The prior art mixing devices have had little or no resistance to reverse air flow, specifically upward air flow.